1. Technical Field
The present invention relates to a semiconductor device.
2. Related Art
In the conventional art, it is known to use trench gates and dummy trenches in semiconductor devices such as an IGBT (see, for example, Japanese Patent Application Publication Nos. 2002-353456, 2009-277792 and 2011-165971. The use of the dummy trenches can increase the injection enhanced effects (the IE effects) for the drift region and reduce the on-voltage.
As the trench gates and dummy trenches become deeper, the IE effects can be increased. Such deep trenches, however, results in a shorter distance between the gate and the collector at the back surface, which increases the collector-gate capacitance. The increased collector-gate capacitance results in increased turn-on power loss and degraded gate controllability.